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Ophthalmology Terms 

Ophthalmology Terms

Harriet S. Meyer

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Ophthalmology Terms

Some of the terms described in this section are specific to ophthalmology, and others have special usage requirements in ophthalmology. See also 11.1, Correct and Preferred Usage of Common Words and Phrases.

adnexa oculi—Although often used as a synonym for eyelids, the term adnexa oculi (which is plural) properly includes the eyelids, lacrimal apparatus, and other appendages of the eye and should be used with its inclusive meaning.

diopter—The diopter is a measure of the power of an optical lens and is the reciprocal of the focal length in meters. Diopter is abbreviated D when used with a number.

diopter sphere

diopter cylinder

conversion from diopters to millimeters

correction of 10.5 D

The prism diopter is a measure of the power of a prism and represents a 1-cm deflection of an image at a distance of 1 m. Its symbol, Δ, may be used with numbers after first mention.

The left eye showed an improvement, with only 25-prism diopter hypotropia.

distance exotropia = 35 prism diopters (Δ); near exotropia = 5Δ

disc; cup-disc ratio—For the optic disc, spell as disc (not disk). The cup-disc ratio refers to the ratio of the diameter of the optic cup (a central area of the optic disc) to the diameter of the optic disc:

cup-disc ratio of 0.6

It can be useful to specify whether the ratio is vertical, horizontal, or other, eg:

The mean horizontal cup-disc ratio by contour estimated from stereo-photography was 0.36 ± 0.18 (mean ± SD).

disc diameters and disc areas—Disc diameters (DD) may be used to indicate location or dimension of findings on the ocular fundus with relative distances expressed as diameters of the optic disc, eg:

2 DD inferior to the fovea

Lesions varied from 0.5 to 4.5 disc diameters (DD; median, 2.0 DD) for the first group, 0.75 to 7.5 DD (median, 2.5 DD) for the second group, and 1.0 to 9.0 DD (median, 4.0 DD) for the last group.

Disc areas (DA) are also used to indicate relative sizes of findings on the ocular fundus, as well as in considerations of the size of the disc, eg:

The scar measured 3 DA.

Significant ischemia was defined as greater than 10 disc areas of retinal capillary nonperfusion.

reduced disc areas (DA) … mean (SD) DA of 2.57 (0.71) mm2

electroretinogram—Waves of the electroretinogram (ERG) are as follows:

a1 a2 b

An ERG may be described as normal, subnormal, or negative. Do not substitute one of these terms for another. (For visual evoked potentials, see 15.11.3, Neurology, Evoked Potentials.) Waves of the pattern electroretinogram (PERG)1 are as follows:

apt bpt cpt

Two main components of the PERG are the P50 wave, a positive-deflection waveform, and the N95 wave, a negative-deflection waveform. The terms P50 and N95 may be used without expansion.

fovea and macula—The central retinal fovea is a central portion of the retinal macula. The terms fovea and macula should be used specifically and not interchangeably.

Goldmann perimetry—This is a method of assessing the visual field. The test stimuli are described by means of a 3-part term: spot size is designated with roman numerals I through V, and luminance is designated with arabic numerals 1 through 4 and letters a through e. For example:

I-4-e isopter area

I-2-e test object

V-4-e light

greatest linear dimension—This is the greatest dimension between 2 points on the boundary of a lesion.

Lesion size was less than or equal to 9 disc areas, and greatest linear dimension was less than or equal to 5400 μm.

injection—When used to indicate excess blood, engorgement, or dilation of a vessel, should be changed to hyperemia or vasodilation, eg, conjunctival hyperemia or conjunctival vasodilation (not conjunctival injection).

intraocular pressure—Measurements of intraocular pressure should include the method used, eg, Goldmann applanation tonometry and, if determined, the corneal thickness measurement.

lasers—Lasers used in ophthalmology include the following:

argon laser

erbium:YAG laser

eximer laser

holmium:YAG laser

krypton laser

Nd:YAG laser

photodynamic therapy laser

Q-switched Nd:YAG laser

transpupillary thermal therapy

The term Nd:YAG (neodymium:yttrium-aluminum-garnet) may be used without expansion.

lidsLids should be changed to eyelids.

maskedMasked, rather than blinded, should be used in the ophthalmologic literature, when referring to randomization, if there could be confusion.

OD, OS, OU—These abbreviations may be used without expansion only with numbers, eg, 20/25 OU, or descriptive assessments of acuity (eg, counting fingers OS; see visual acuity, vision):





oculus dexter

right eye


oculus sinister

left eye


oculus uterque

each eye

Note that OU does not mean both eyes, although it is often used incorrectly to imply a vision measurement (eg, visual acuity or visual field) with both eyes at the same time.

See also visual acuity, vision, below.

orbitOrbit refers to the bony cavity that contains the eyeball and its adnexa (muscles, vessels, nerves). It should be clear to readers whether authors are referring to the orbit, the specific bones that compose it, the structures that fill the orbit, or a combination of these.

visual acuity, vision—Distinguish between vision, a general term, and visual acuity, measurable clearness of vision. If a measurement is given, eg, 20/20 (see below), use “visual acuity.” Change “unaided vision” to “acuity without correction.” (See also 11.0, Correct and Preferred Usage.)

distance acuity—The Snellen eye chart is a well-known method of assessing distance visual acuity, resulting in the Snellen fraction, an expression such as 20/20, 20/15, or 20/60. The first number represents the testing distance from chart to patient; the second number represents the smallest row of letters that the patient can read. For example, acuity of 20/40 indicates that at 20 ft the smallest line read is readable by a normal eye at 40 ft.

The units for distance acuity are feet (eg, 20 ft) or meters (eg, 6 m). By convention, acuity is expressed without these units specified, eg, 20/20. JAMA and the Archives Journals follow the author’s preference in expressing distance acuity equivalents as metric, eg, 6/6, or English, eg, 20/20, and do not convert English fractions to metric or vice versa. Only one type, English or metric, should be used throughout a manuscript.

Visual acuity is assessed separately for each eye. Other means are also used to assess visual acuity, eg, counting fingers (CF), hand motions (HM), and light perception (LP), which is indicated as LP with projection, LP without projection, or no LP (NLP). Express visual acuity, including numerical measures and other means, by using OD or RE (right eye) and OS or LE (left eye). (See also OD, OS, OU, above).

The visual acuity was 20/40 OD and counting fingers OS.

(Not:…20/40 OD and counting fingers in the left eye.)

Another method of assessing visual acuity makes use of the Bailey-Lovie acuity chart and designates acuity using the base 10 logarithm of the minimum angle of resolution, or logMAR. A logMAR of 0.0 is equivalent to 20/20 Snellen. LogMAR visual acuities always should be expressed in logMAR.

near visual acuity—Near visual acuity (reading vision) may be reported by means of Snellen equivalents or the Jaeger system (J values), eg, J7. J1 is equivalent to Snellen 20/23.2

visual field—The extent of the visual field is described by means of degrees from a central point from 0° through 90°:

85° temporally

65° nasally

56° up and nasally

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